1. Field of the Invention
The present invention concerns the use of a Rogowski coil as described in U.S. patent application Ser. No. 08/067628 filed 28 May 1993now U.S. Pat. No. 5,414,400.
2. Description of the Prior Art
A coil of this kind comprises at least one printed circuit plate provided with a circular cutout, the coil being implemented by rectilinear metal deposits on each of the two faces of the plate and extending along radii such that geometrical projections thereof intersect at the center of said cutout, electrical connections between the radii on one face and those on the opposite face being implemented by plated-through holes that pass through the thickness of the plate.
A coil of this kind has perfect axial symmetry. The winding constituted by the radii and the holes comprises an outward leg and a return leg around the circular cutout with an input and an output on the same side on the plate separated by a distance of a few tenths of a millimeter. A coil of this kind is also relatively insensitive to temperature variations because the material supporting the winding is epoxy resin.
A first object of the invention is a simple way of using a coil of this kind to produce a current measuring device that is substantially insensitive to temperature variations.
Another object of the invention is to provide a temperature measuring device using a Rogowski coil of this kind.
Current is usually measured by means of a Rogowski coil by loading the coil with a high value resistor, measuring the voltage across this resistor and integrating this voltage. The invention utilizes this method, employing a particular value of the load resistor which renders the measurement substantially independent of temperature.
The temperature is measured by using the Rogowski coil winding as one arm of a Wheatstone bridge.